O14 - Varying Host Response in Different Low-Lethality Models of Murine Abdominal Sepsis

Lori Gentile, Dina Nacionales, M. Cecilia Lopez, Angela Cuenca, Alex Cuenca, Benjamin Szpila, Ricardo Ungaro, Shawn Larson, Christiaan Leeuwenburgh, Frederick Moore, Henry Baker, Lyle Moldawer, Philip Efron, University of Florida College of Medicine

Background: Animal models for the study of sepsis are being increasingly scrutinized. However, they remain essential for early translational research. In this report, we examined two different low-lethality murine models (20-40%) of polymicrobial intra-abdominal sepsis at the level of the leukocyte transcriptome, and explored their overall effects on genes involved in innate and adaptive immunity.

Hypothesis: We hypothesized that the cecal slurry (CS) model of sepsis would have more robust early inflammatory changes, whereas the cecal ligation and puncture (CLP) model would show greater changes involving adaptive immune suppression. 

Methods: 6-10 week old male C57BL/6j mice underwent either the ‘gold standard’ CLP model of intra-abdominal sepsis or the CS model of intra-abdominal sepsis, where cecal contents are injected i.p. Surviving mice were euthanized at 2 hrs, 1 or 3 days after sepsis. Whole blood was collected, and total RNA was isolated. Genome-wide expression analysis was performed on total blood leukocytes and expression patterns were compared between healthy control mice and septic mice (p<0.001). Functional pathway analysis was performed using Ingenuity Pathway Analysis.

Results: We found that the murine leukocyte transcriptomic response to CLP and CS models of sepsis were genomically dissimilar at 2 hours, 1, and 3 days after sepsis, with changes in gene expression in less than 1/3 of the probe sets overlapping. The Pearson correlation coefficient for the maximum change in expression for probe sets that changed significantly over time (n=19,071) was R=0.545 (R2=0.297). The CS model resulted in a greater magnitude of inflammatory gene expression changes in response to sepsis with an associated increased production of inflammatory chemokines and cytokines. Two hours after sepsis, the CLP pathway had more significant expression of genes associated with IL-10 signaling, whereas the CS pathway had greater expression of genes related to CD28, apoptosis, IL-1, and T-cell receptor signaling. By 3 days, the changes in gene expression from all pathways were returning to baseline in both the CS and CLP models.

Conclusions: These analyses reveal that the murine blood leukocyte response to sepsis is markedly different depending on which model of intra-abdominal sepsis is employed, despite similar lethalities. Whereas the CS model favors the early pro-inflammatory changes, the CLP model is more evident of adaptive immune suppression.